This invention relates generally to local networks in a vehicle and, more particularly, to efficiently transmitting data over a local network in a vehicle with several network subscribers distributed over the vehicle.
The implementation of a local network in a vehicle is well known. One conventional approach to using a local network in a vehicle is disclosed in German Patent Specification DE 195 03 213 C1. Typically, such local networks have several network nodes, referred to herein as subscribers. Some of the subscribers generate audio data, video data, and control data, and transmit the data over the network. Such subscribers are referred to herein as data sources. Other subscribers on the network receive data from the network and reproduce the data. Such data reproduction can be, for example, an acoustic or visual reproduction. These subscribers are referred to herein as data sinks.
Such conventional vehicle-hosted local networks have various equipment that serve as data sources. Examples of such equipment include, for example, a car radio, CD player, video recorder, TV tuner, etc. Such devices conduct their data uncompressed to appropriate data sinks via a data line of the network. The data sinks can be, for example, an audio amplifier to which several loudspeakers are connected, or a display screen which displays an uncompressed BAS video signal. Typically, the video and audio data are transmitted separately and concurrently. For example, a TV tuner data source transmits audio, video and control data over the local network. The video data are transmitted to a screen, in the manner described above, as uncompressed FBAS video signals. In parallel to this, the audio data are transmitted to an audio amplifier as uncompressed audio data and are reproduced as acoustic signals. Typically, the audio and video data are transmitted in a format that prescribes a clocked sequence of individual bit groups of the same length. In these bit groups, specific bit positions for transmission from the data source to the data sink are prescribed for the audio and video data, together referred to as real-time-relevant source data. Real-time-relevant source data are not accessible to an interruption of the data flow. Specific bit positions are also prescribed for the control data, if present. The bit positions for the source data are collected together in several connected partial picture groups, by means of which the specific audio and video data of a data source are transmitted in parallel to an associated data sink. This transmission is organized by control data that are transmitted in parallel with the audio and video data. The subscribers on such a network can input their data into the network or take their data from it independently of one another and sometimes simultaneously. Such a network can accommodate only a few subscribers, since the transmission capacity of the network over the data line is limited.
What is needed, therefore, is a local network for use in a vehicle that substantially utilizes the maximum transmission capacity while maintaining the quality of data display in the data sinks.